A dispenser supplying a predetermined amount of liquid that is in liquid form, such as water, oil, or resin is used in various fields such as in a semiconductor process or in the medical field.
Particularly in a semiconductor process, a dispenser is frequently used in an underfill process to fill a package of a semiconductor device with a resin. In a process of manufacturing a light emitting diode (LED) device, a dispenser is used in a process of coating a LED chip of the LED device with a phosphorescent liquid in which a phosphorescent material and a resin are mixed.
The dispenser as described above includes, as a core element, a pump that receives a liquid and dispenses a fixed amount of the liquid to an exact position.
Various pumps structures such as a screw pump or a linear pump are available. Recently, a piezoelectric pump that uses a piezoelectric element as an actuator has been developed and used in a semiconductor process or the like to perform a dispensing operation at a high speed.
KR 2005-0079557 (published on Aug. 10, 2005) discloses a piezoelectric pump structure comprising a plurality of piezoelectric actuators, on which a piezoelectric element is attached and which are sequentially operated in connection with one another at different displacement differences to pump a fluid.
A piezoelectric actuator used in a piezoelectric pump is usually formed of a ceramic material. When a ceramic piezoelectric actuator as described above is used for a long period time, fatigue destruction is generated. If fatigue destruction is generated in a piezoelectric actuator during an operation of dispensing a liquid to a semiconductor device by using a piezoelectric pump, the liquid may not be dispensed or a dispensing amount of the liquid may be not accurate and process defects may be caused.
Thus, a technique of predicting fatigue destruction of the piezoelectric actuator and effectively controlling the same is required.